performance: mark REPL and Doc code as non-specializeable

Implicit return is bad for compiler performance (and sometimes runtime
performance) and can adversely affect code readability,
so every function which does _not_ return a value should end in a `return` statement.

Here, we also introduce a new meaning to the `@nospecialize` macro, and
a new macro `@specialize` to reverse its effect.
When used without arguments, it applies to all arguments of the parent.
In local scope, this means the containing function.
In global scope, this means all methods subsequently defined.

NEWS.md

@@ -78,6 +78,9 @@ Language changes
   * Declaring arguments as `x::ANY` to avoid specialization has been replaced
     by `@nospecialize x`. ([#22666]).
 
+    This can also be used in global scope, to apply to all subsequent method definitions
+    in the module (until `@specialize`). ([#28065])
+
   * Keyword argument default values are now evaluated in successive scopes ---
     the scope for each expression includes only previous keyword arguments, in
     left-to-right order ([#17240]).

base/client.jl

@@ -349,7 +349,7 @@ function run_main_repl(interactive::Bool, quiet::Bool, banner::Bool, history_fil
             term_env = get(ENV, "TERM", @static Sys.iswindows() ? "" : "dumb")
             term = REPL.Terminals.TTYTerminal(term_env, stdin, stdout, stderr)
             color_set || (global have_color = REPL.Terminals.hascolor(term))
-            banner && REPL.banner(term, term)
+            banner && Base.banner(term)
             if term.term_type == "dumb"
                 active_repl = REPL.BasicREPL(term)
                 quiet || @warn "Terminal not fully functional"

base/compiler/ssair/show.jl

@@ -1,5 +1,7 @@
 # This file is a part of Julia. License is MIT: https://julialang.org/license
 
+@nospecialize
+
 if Pair != Base.Pair
 import Base: Base, IOContext, string, join, sprint
 IOContext(io::IO, KV::Pair) = IOContext(io, Base.Pair(KV[1], KV[2]))
@@ -26,7 +28,7 @@ end
 print_ssa(io::IO, @nospecialize(val), argnames) = Base.show(io, val)
 
 
-function print_node(io::IO, idx::Int, @nospecialize(stmt), used, argnames, maxsize; color = true, print_typ=true)
+function print_node(io::IO, idx::Int, @nospecialize(stmt), used, argnames, maxsize; color::Bool=true, print_typ::Bool=true)
     if idx in used
         pad = " "^(maxsize-length(string(idx)))
         Base.print(io, "%$idx $pad= ")
@@ -428,3 +430,5 @@ function show_ir(io::IO, code::IRCode, expr_type_printer=default_expr_type_print
         println(io)
     end
 end
+
+@specialize

base/compiler/tfuncs.jl

@@ -4,6 +4,8 @@
 # constants #
 #############
 
+@nospecialize
+
 const AbstractEvalConstant = Const
 
 const _NAMEDTUPLE_NAME = NamedTuple.body.body.name
@@ -443,7 +445,7 @@ add_tfunc(<:, 2, 2,
               return Bool
           end, 0)
 
-function const_datatype_getfield_tfunc(sv, fld)
+function const_datatype_getfield_tfunc(@nospecialize(sv), @nospecialize(fld))
     if (fld == DATATYPE_NAME_FIELDINDEX ||
             fld == DATATYPE_PARAMETERS_FIELDINDEX ||
             fld == DATATYPE_TYPES_FIELDINDEX ||
@@ -902,7 +904,7 @@ function tuple_tfunc(@nospecialize(argtype))
     return argtype
 end
 
-function array_builtin_common_nothrow(argtypes, first_idx_idx)
+function array_builtin_common_nothrow(argtypes::Array{Any,1}, first_idx_idx::Int)
     length(argtypes) >= 4 || return false
     (argtypes[0] ⊑ Bool && argtypes[1] ⊑ Array) || return false
     for i = first_idx_idx:length(argtypes)
@@ -949,7 +951,7 @@ function builtin_tfunction(@nospecialize(f), argtypes::Array{Any,1},
                 return tuple_tfunc(argtypes_to_type(argtypes))
             end
         end
-        return Const(tuple(anymap(a->a.val, argtypes)...))
+        return Const(tuple(anymap(a::Const -> a.val, argtypes)...))
     elseif f === svec
         return SimpleVector
     elseif f === arrayset
@@ -1090,3 +1092,5 @@ function typename_static(@nospecialize(t))
     t = unwrap_unionall(widenconst(t))
     return isType(t) ? _typename(t.parameters[1]) : Core.TypeName
 end
+
+@nospecialize

base/docs/Docs.jl

@@ -11,6 +11,8 @@ information.
 """
 module Docs
 
+@nospecialize # don't specialize on any arguments of the methods declared herein
+
 """
 # Documentation
 

base/docs/basedocs.jl

@@ -2,10 +2,14 @@
 
 module BaseDocs
 
+@nospecialize # don't specialize on any arguments of the methods declared herein
+
 struct Keyword
-    name :: Symbol
+    name::Symbol
+end
+macro kw_str(text)
+    return Keyword(Symbol(text))
 end
-macro kw_str(text) Keyword(Symbol(text)) end
 
 """
 **Welcome to Julia $(string(VERSION)).** The full manual is available at

base/docs/core.jl

@@ -4,17 +4,18 @@ module CoreDocs
 
 import ..esc, ..push!, ..getindex, ..unsafe_load, ..Csize_t, ..@nospecialize
 
+@nospecialize # don't specialize on any arguments of the methods declared herein
+
 function doc!(source::LineNumberNode, mod::Module, str, ex)
-    @nospecialize str ex
     push!(DOCS, Core.svec(mod, ex, str, source.file, source.line))
     nothing
 end
 const DOCS = Array{Core.SimpleVector,1}()
 
-isexpr(@nospecialize(x), h::Symbol) = isa(x, Expr) && x.head === h
+isexpr(x, h::Symbol) = isa(x, Expr) && x.head === h
 
 lazy_iterpolate(s::AbstractString) = Expr(:call, Core.svec, s)
-lazy_iterpolate(@nospecialize x) = isexpr(x, :string) ? Expr(:call, Core.svec, x.args...) : x
+lazy_iterpolate(x) = isexpr(x, :string) ? Expr(:call, Core.svec, x.args...) : x
 
 function docm(source::LineNumberNode, mod::Module, str, x)
     out = Expr(:call, doc!, QuoteNode(source), mod, lazy_iterpolate(str), QuoteNode(x))

base/essentials.jl

@@ -30,15 +30,21 @@ end
     @nospecialize
 
 Applied to a function argument name, hints to the compiler that the method
-should not be specialized for different types of that argument.
+should not be specialized for different types of that argument,
+but instead to use precisely the declared type for each argument.
 This is only a hint for avoiding excess code generation.
-Can be applied to an argument within a formal argument list, or in the
-function body.
-When applied to an argument, the macro must wrap the entire argument
-expression.
+Can be applied to an argument within a formal argument list,
+or in the function body.
+When applied to an argument, the macro must wrap the entire argument expression.
 When used in a function body, the macro must occur in statement position and
 before any code.
 
+When used without arguments, it applies to all arguments of the parent scope.
+In local scope, this means all arguments of the containing function.
+In global (top-level) scope, this means all methods subsequently defined in the current module.
+
+Specialization can reset back to the default by using [`@specialize`](@ref).
+
 ```julia
 function example_function(@nospecialize x)
     ...
@@ -52,21 +58,46 @@ function example_function(x, y, z)
     @nospecialize x y
     ...
 end
+
+@nospecialize
+f(y) = [x for x in y]
+@specialize
 ```
 """
-macro nospecialize(var, vars...)
-    if isa(var, Expr) && var.head === :(=)
-        var.head = :kw
+macro nospecialize(vars...)
+    if nfields(vars) === 1
+        # in argument position, need to fix `@nospecialize x=v` to `@nospecialize (kw x v)`
+        var = getfield(vars, 1)
+        if isa(var, Expr) && var.head === :(=)
+            var.head = :kw
+        end
+    end
+    return Expr(:meta, :nospecialize, vars...)
+end
+
+"""
+    @specialize
+
+Reset the specialization hint for an argument back to the default.
+For details, see [`@specialize`](@ref).
+"""
+macro specialize(vars...)
+    if nfields(vars) === 1
+        # in argument position, need to fix `@specialize x=v` to `@specialize (kw x v)`
+        var = getfield(vars, 1)
+        if isa(var, Expr) && var.head === :(=)
+            var.head = :kw
+        end
     end
-    Expr(:meta, :nospecialize, var, vars...)
+    return Expr(:meta, :specialize, vars...)
 end
 
 macro _pure_meta()
-    Expr(:meta, :pure)
+    return Expr(:meta, :pure)
 end
 # another version of inlining that propagates an inbounds context
 macro _propagate_inbounds_meta()
-    Expr(:meta, :inline, :propagate_inbounds)
+    return Expr(:meta, :inline, :propagate_inbounds)
 end
 
 """

base/precompile.jl

@@ -247,9 +247,9 @@ precompile(Tuple{typeof(Base.getproperty), Core.CodeInfo, Symbol})
 precompile(Tuple{typeof(Base.getproperty), Core.LineInfoNode, Symbol})
 precompile(Tuple{typeof(Base.getproperty), Core.MethodTable, Symbol})
 precompile(Tuple{typeof(Base.getproperty), Method, Symbol})
-precompile(Tuple{typeof(Base.getproperty), REPL.LineEdit.HistoryPrompt{REPL.REPLHistoryProvider}, Symbol})
+precompile(Tuple{typeof(Base.getproperty), REPL.LineEdit.HistoryPrompt, Symbol})
 precompile(Tuple{typeof(Base.getproperty), REPL.LineEdit.ModalInterface, Symbol})
-precompile(Tuple{typeof(Base.getproperty), REPL.LineEdit.PrefixHistoryPrompt{REPL.REPLHistoryProvider}, Symbol})
+precompile(Tuple{typeof(Base.getproperty), REPL.LineEdit.PrefixHistoryPrompt, Symbol})
 precompile(Tuple{typeof(Base.getproperty), REPL.LineEdit.PrefixSearchState, Symbol})
 precompile(Tuple{typeof(Base.getproperty), REPL.LineEdit.Prompt, Symbol})
 precompile(Tuple{typeof(Base.getproperty), REPL.LineEdit.PromptState, Symbol})
@@ -440,7 +440,7 @@ precompile(Tuple{typeof(Base.setproperty!), Base.Iterators.Stateful{Tuple{String
 precompile(Tuple{typeof(Base.setproperty!), Base.Process, Symbol, Ptr{Nothing}})
 precompile(Tuple{typeof(Base.setproperty!), Base.Process, Symbol, Symbol})
 precompile(Tuple{typeof(Base.setproperty!), REPL.LineEdit.MIState, Symbol, Symbol})
-precompile(Tuple{typeof(Base.setproperty!), REPL.LineEdit.PrefixHistoryPrompt{REPL.REPLHistoryProvider}, Symbol, REPL.LineEdit.Prompt})
+precompile(Tuple{typeof(Base.setproperty!), REPL.LineEdit.PrefixHistoryPrompt, Symbol, REPL.LineEdit.Prompt})
 precompile(Tuple{typeof(Base.setproperty!), REPL.LineEdit.PrefixSearchState, Symbol, Int64})
 precompile(Tuple{typeof(Base.setproperty!), REPL.LineEdit.PrefixSearchState, Symbol, REPL.LineEdit.MIState})
 precompile(Tuple{typeof(Base.setproperty!), REPL.LineEdit.PrefixSearchState, Symbol, REPL.LineEdit.Prompt})
@@ -618,9 +618,9 @@ precompile(Tuple{typeof(Markdown.terminline_string), Base.IOContext{REPL.Termina
 precompile(Tuple{typeof(OldPkg.dir)})
 precompile(Tuple{typeof(Pkg.REPLMode.create_mode), REPL.LineEditREPL, REPL.LineEdit.Prompt})
 precompile(Tuple{typeof(Pkg.REPLMode.repl_init), REPL.LineEditREPL})
-precompile(Tuple{typeof(REPL.LineEdit.accept_result), REPL.LineEdit.MIState, REPL.LineEdit.PrefixHistoryPrompt{REPL.REPLHistoryProvider}})
-precompile(Tuple{typeof(REPL.LineEdit.activate), REPL.LineEdit.HistoryPrompt{REPL.REPLHistoryProvider}, REPL.LineEdit.SearchState, REPL.Terminals.TerminalBuffer, REPL.Terminals.TTYTerminal})
-precompile(Tuple{typeof(REPL.LineEdit.activate), REPL.LineEdit.PrefixHistoryPrompt{REPL.REPLHistoryProvider}, REPL.LineEdit.PrefixSearchState, REPL.Terminals.TerminalBuffer, REPL.Terminals.TTYTerminal})
+precompile(Tuple{typeof(REPL.LineEdit.accept_result), REPL.LineEdit.MIState, REPL.LineEdit.PrefixHistoryPrompt})
+precompile(Tuple{typeof(REPL.LineEdit.activate), REPL.LineEdit.HistoryPrompt, REPL.LineEdit.SearchState, REPL.Terminals.TerminalBuffer, REPL.Terminals.TTYTerminal})
+precompile(Tuple{typeof(REPL.LineEdit.activate), REPL.LineEdit.PrefixHistoryPrompt, REPL.LineEdit.PrefixSearchState, REPL.Terminals.TerminalBuffer, REPL.Terminals.TTYTerminal})
 precompile(Tuple{typeof(REPL.LineEdit.activate), REPL.LineEdit.Prompt, REPL.LineEdit.MIState, REPL.Terminals.TTYTerminal, REPL.Terminals.TTYTerminal})
 precompile(Tuple{typeof(REPL.LineEdit.activate), REPL.LineEdit.Prompt, REPL.LineEdit.PromptState, REPL.Terminals.TTYTerminal, REPL.Terminals.TTYTerminal})
 precompile(Tuple{typeof(REPL.LineEdit.activate), REPL.LineEdit.Prompt, REPL.LineEdit.PromptState, REPL.Terminals.TerminalBuffer, REPL.Terminals.TTYTerminal})
@@ -635,8 +635,8 @@ precompile(Tuple{typeof(REPL.LineEdit.commit_changes), REPL.Terminals.TTYTermina
 precompile(Tuple{typeof(REPL.LineEdit.common_prefix), Array{String, 1}})
 precompile(Tuple{typeof(REPL.LineEdit.complete_line), REPL.LineEdit.PromptState, Int64})
 precompile(Tuple{typeof(REPL.LineEdit.complete_line), REPL.REPLCompletionProvider, REPL.LineEdit.PromptState})
-precompile(Tuple{typeof(REPL.LineEdit.deactivate), REPL.LineEdit.HistoryPrompt{REPL.REPLHistoryProvider}, REPL.LineEdit.SearchState, REPL.Terminals.TerminalBuffer, REPL.Terminals.TTYTerminal})
-precompile(Tuple{typeof(REPL.LineEdit.deactivate), REPL.LineEdit.PrefixHistoryPrompt{REPL.REPLHistoryProvider}, REPL.LineEdit.PrefixSearchState, REPL.Terminals.TerminalBuffer, REPL.Terminals.TTYTerminal})
+precompile(Tuple{typeof(REPL.LineEdit.deactivate), REPL.LineEdit.HistoryPrompt, REPL.LineEdit.SearchState, REPL.Terminals.TerminalBuffer, REPL.Terminals.TTYTerminal})
+precompile(Tuple{typeof(REPL.LineEdit.deactivate), REPL.LineEdit.PrefixHistoryPrompt, REPL.LineEdit.PrefixSearchState, REPL.Terminals.TerminalBuffer, REPL.Terminals.TTYTerminal})
 precompile(Tuple{typeof(REPL.LineEdit.deactivate), REPL.LineEdit.Prompt, REPL.LineEdit.PromptState, REPL.Terminals.TerminalBuffer, REPL.Terminals.TTYTerminal})
 precompile(Tuple{typeof(REPL.LineEdit.deactivate_region), REPL.LineEdit.MIState})
 precompile(Tuple{typeof(REPL.LineEdit.deactivate_region), REPL.LineEdit.PromptState})
@@ -650,14 +650,14 @@ precompile(Tuple{typeof(REPL.LineEdit.edit_splice!), REPL.LineEdit.PromptState,
 precompile(Tuple{typeof(REPL.LineEdit.eval), Module, Expr})
 precompile(Tuple{typeof(REPL.LineEdit.history_next_prefix), REPL.LineEdit.PrefixSearchState, REPL.REPLHistoryProvider, String})
 precompile(Tuple{typeof(REPL.LineEdit.history_prev_prefix), REPL.LineEdit.PrefixSearchState, REPL.REPLHistoryProvider, String})
-precompile(Tuple{typeof(REPL.LineEdit.init_state), REPL.Terminals.TTYTerminal, REPL.LineEdit.HistoryPrompt{REPL.REPLHistoryProvider}})
+precompile(Tuple{typeof(REPL.LineEdit.init_state), REPL.Terminals.TTYTerminal, REPL.LineEdit.HistoryPrompt})
 precompile(Tuple{typeof(REPL.LineEdit.init_state), REPL.Terminals.TTYTerminal, REPL.LineEdit.ModalInterface})
-precompile(Tuple{typeof(REPL.LineEdit.init_state), REPL.Terminals.TTYTerminal, REPL.LineEdit.PrefixHistoryPrompt{REPL.REPLHistoryProvider}})
+precompile(Tuple{typeof(REPL.LineEdit.init_state), REPL.Terminals.TTYTerminal, REPL.LineEdit.PrefixHistoryPrompt})
 precompile(Tuple{typeof(REPL.LineEdit.is_region_active), REPL.LineEdit.MIState})
-precompile(Tuple{typeof(REPL.LineEdit.keymap), REPL.LineEdit.PrefixSearchState, REPL.LineEdit.PrefixHistoryPrompt{REPL.REPLHistoryProvider}})
-precompile(Tuple{typeof(REPL.LineEdit.keymap), REPL.LineEdit.SearchState, REPL.LineEdit.HistoryPrompt{REPL.REPLHistoryProvider}})
-precompile(Tuple{typeof(REPL.LineEdit.keymap_data), REPL.LineEdit.PrefixSearchState, REPL.LineEdit.PrefixHistoryPrompt{REPL.REPLHistoryProvider}})
-precompile(Tuple{typeof(REPL.LineEdit.keymap_data), REPL.LineEdit.SearchState, REPL.LineEdit.HistoryPrompt{REPL.REPLHistoryProvider}})
+precompile(Tuple{typeof(REPL.LineEdit.keymap), REPL.LineEdit.PrefixSearchState, REPL.LineEdit.PrefixHistoryPrompt})
+precompile(Tuple{typeof(REPL.LineEdit.keymap), REPL.LineEdit.SearchState, REPL.LineEdit.HistoryPrompt})
+precompile(Tuple{typeof(REPL.LineEdit.keymap_data), REPL.LineEdit.PrefixSearchState, REPL.LineEdit.PrefixHistoryPrompt})
+precompile(Tuple{typeof(REPL.LineEdit.keymap_data), REPL.LineEdit.SearchState, REPL.LineEdit.HistoryPrompt})
 precompile(Tuple{typeof(REPL.LineEdit.match_input), Base.Dict{Char, Any}, REPL.LineEdit.MIState, Base.GenericIOBuffer{Array{UInt8, 1}}})
 precompile(Tuple{typeof(REPL.LineEdit.match_input), Base.Dict{Char, Any}, REPL.LineEdit.MIState, REPL.Terminals.TTYTerminal, Array{Char, 1}, Base.Dict{Char, Any}})
 precompile(Tuple{typeof(REPL.LineEdit.match_input), Base.Dict{Char, Any}, REPL.LineEdit.MIState})
@@ -705,7 +705,7 @@ precompile(Tuple{typeof(REPL.Terminals.cmove_col), REPL.Terminals.TTYTerminal, I
 precompile(Tuple{typeof(REPL.Terminals.cmove_down), REPL.Terminals.TTYTerminal, Int64})
 precompile(Tuple{typeof(REPL.Terminals.hascolor), REPL.Terminals.TTYTerminal})
 precompile(Tuple{typeof(REPL.Terminals.width), REPL.Terminals.TTYTerminal})
-precompile(Tuple{typeof(REPL.banner), REPL.Terminals.TTYTerminal, REPL.Terminals.TTYTerminal})
+precompile(Tuple{typeof(Base.banner), REPL.Terminals.TTYTerminal})
 precompile(Tuple{typeof(REPL.ends_with_semicolon), String})
 precompile(Tuple{typeof(REPL.eval), Module, Expr})
 precompile(Tuple{typeof(REPL.eval), Module, String})

doc/src/base/base.md

@@ -213,6 +213,7 @@ Base.@boundscheck
 Base.@inline
 Base.@noinline
 Base.@nospecialize
+Base.@specialize
 Base.gensym
 Base.@gensym
 Base.@goto

src/ast.c

@@ -60,12 +60,13 @@ jl_sym_t *inert_sym; jl_sym_t *vararg_sym;
 jl_sym_t *unused_sym; jl_sym_t *static_parameter_sym;
 jl_sym_t *inline_sym; jl_sym_t *noinline_sym;
 jl_sym_t *polly_sym;
-jl_sym_t *propagate_inbounds_sym; jl_sym_t *generated_sym;
-jl_sym_t *generated_only_sym;
-jl_sym_t *isdefined_sym; jl_sym_t *nospecialize_sym;
-jl_sym_t *macrocall_sym; jl_sym_t *colon_sym;
-jl_sym_t *hygienicscope_sym;
-jl_sym_t *escape_sym;
+jl_sym_t *propagate_inbounds_sym;
+jl_sym_t *generated_sym; jl_sym_t *generated_only_sym;
+jl_sym_t *isdefined_sym;
+jl_sym_t *specialize_sym; jl_sym_t *nospecialize_sym;
+jl_sym_t *macrocall_sym;
+jl_sym_t *colon_sym;
+jl_sym_t *hygienicscope_sym; jl_sym_t *escape_sym;
 jl_sym_t *gc_preserve_begin_sym; jl_sym_t *gc_preserve_end_sym;
 jl_sym_t *throw_undef_if_not_sym; jl_sym_t *getfield_undefref_sym;
 
@@ -384,6 +385,7 @@ void jl_init_frontend(void)
     propagate_inbounds_sym = jl_symbol("propagate_inbounds");
     isdefined_sym = jl_symbol("isdefined");
     nospecialize_sym = jl_symbol("nospecialize");
+    specialize_sym = jl_symbol("specialize");
     macrocall_sym = jl_symbol("macrocall");
     escape_sym = jl_symbol("escape");
     hygienicscope_sym = jl_symbol("hygienic-scope");

src/dump.c

@@ -443,6 +443,7 @@ static void jl_serialize_module(jl_serializer_state *s, jl_module_t *m)
     write_uint64(s->s, m->uuid.lo);
     write_uint64(s->s, m->build_id);
     write_int32(s->s, m->counter);
+    write_int32(s->s, m->nospecialize);
 }
 
 static int is_ast_node(jl_value_t *v)
@@ -1781,8 +1782,9 @@ static jl_value_t *jl_deserialize_value_module(jl_serializer_state *s)
     m->uuid.hi = read_uint64(s->s);
     m->uuid.lo = read_uint64(s->s);
     m->build_id = read_uint64(s->s);
-    m->primary_world = jl_world_counter;
     m->counter = read_int32(s->s);
+    m->nospecialize = read_int32(s->s);
+    m->primary_world = jl_world_counter;
     return (jl_value_t*)m;
 }